1. Field of the Invention
The present invention relates to packaged food articles, specifically articles where a food product is cooked after being packaged.
2. Background of the Invention
Many food products are processed in thermoplastic film packages by subjecting the packaged product to elevated temperatures produced by, for example, immersion in hot water or exposure to steam. Such thermal processing often is referred to as cook-in, and films used in such processes are known as cook-in films.
A food product that is packaged and processed in this manner can be refrigerated, shipped, and stored until the food product is to be consumed or, for example, sliced and repackaged into smaller portions for retail display. Many sliced luncheon meats are processed in this fashion. Alternatively, the processed food can be removed immediately from the cook-in package for consumption or further processing (e.g., sliced and repackaged).
A cook-in film must be capable of withstanding exposure to rather severe temperature conditions for extended periods of time while not compromising its ability to contain the food product. Cook-in processes typically involve a long cook cycle. Submersion in hot (i.e., about 55xc2x0 to 65xc2x0 C.) water for up to about 4 hours is common; submersion in 70xc2x0 to 100xc2x0 C. water or exposure to steam for up to 12 hours is not uncommon, although most cook-in procedures normally do not involve temperatures in excess of about 90xc2x0 C. During such extended periods of time at elevated temperatures, any seams in a package formed from a cook-in film preferably resist failure (i.e., pulling apart).
The cook-in film preferably possesses sufficient adherence to the food product to inhibit or prevent xe2x80x9ccook-outxe2x80x9d (sometimes referred to as xe2x80x9cpurgexe2x80x9d), which is water and/or juices that collect between the surface of the contained food product and the food-contact surface of the packaging material during the cook-in process. Preventing cook-out can increase product yield, provide a better tasting product, improve shelf life and provide a more aesthetically appealing packaged product. Films that adhere well to the packaged food product help reduce cook-out.
Many cook-in films are corona treated to increase the surface energy of their food-contact layers. However, corona treatment can be inconsistent, can result in a film with inconsistent adhesion, can result in a film having a surface energy that decays over time, and can interfere with the sealability of a film.
Following the cook-in process, the film or package preferably conforms, if not completely then at least substantially, to the shape of the contained food product. Often, this is achieved by allowing the film to heat shrink under cook-in conditions so as to form a tightly fitting package. In other words, the cook-in film desirably possesses sufficient shrink energy such that the amount of thermal energy used to cook the food product also is adequate to shrink the packaging film snugly around the contained product. Alternatively, the cook-in film package can be caused to shrink around the contained food product prior to initiating the cook-in procedure by, for example, placing the package in a heated environment prior to cooking.
Some presently available cook-in films adhere well with the meat product and do a good job of reducing cook-out. Additionally, most such films are able to withstand extended time periods at the elevated temperatures described supra; accordingly such films are adequate for many cook-in applications. However, some cook-in applications impose even more stringent performance requirements. For example, some food products that are processed via cook-in procedures are oxygen sensitive. Cook-in films for these products need to include one or more oxygen barrier layers. Other cook-in applications require that the film or the package made therefrom be printable and be able to retain any image printed thereon.
An increasingly important requirement of cook-in films is that they provide an aesthetically pleasing packaged food product. For example, as mentioned previously, the cook-in film generally shrinks until it at least substantially conforms to the shape of the enclosed food product; however, unless the shape of that food product is itself aesthetically pleasing, the resulting packaged food article does not have an aesthetically pleasing shape.
Because pre-forming the food article prior to packaging is impractical (and often impossible), providing a cook-in film that can provide a resulting packaged food article with an aesthetically pleasing shape is highly desirable.
Briefly, the present invention provides a packaged food article which includes a meat product and a thermoplastic, heat shrinkable film. The film includes a meat-contact layer that contains a polymer which includes mer units derived from a C2-C4 xcex1-olefin. The film is sealed so as to form a bag which encloses the meat product. At least one sealed edge of the bag defines an arc which includes at least four segments. Each of the segments has a radius of curvature which differs from the radius of curvature of any adjoining segment.
When the packaged food article is subjected to a temperature of from about 50xc2x0 C. up to about the Vicat softening point of the meat-contact layer polymer that includes mer units derived from a C2-C4 xcex1-olefin, preferably up to about 100xc2x0 C., the packaged food article advantageously takes the general shape of, for example, a poultry breast. Because the arc of the bag edge includes at least four segments with varying radii of curvature, the general shape of the packaged food article is not essentially spherical. Rather, the packaged food article has a more irregular, yet generally rounded appearance such as is observed in actual poultry breasts.
To assist in understanding the more detailed description of the invention that follows, certain definitions are provided immediately below. These definitions apply hereinthroughout unless a contrary intention is explicitly indicated:
xe2x80x9cpolymerxe2x80x9d means the polymerization product of one or more monomers and is inclusive of homopolymers as well as copolymers, terpolymers, tetrapolymers, etc., and blends and modifications of any of the foregoing;
xe2x80x9cmer unitxe2x80x9d means that portion of a polymer derived from a single reactant molecule; for example, a mer unit from ethylene has the general formula xe2x80x94CH2CH2xe2x80x94;
xe2x80x9chomopolymerxe2x80x9d means a polymer consisting essentially of a single type of repeating mer unit;
xe2x80x9ccopolymerxe2x80x9d means a polymer that includes mer units derived from two reactants (normally monomers) and is inclusive of random, block, segmented, graft, etc., copolymers;
xe2x80x9cinterpolymerxe2x80x9d means a polymer that includes mer units derived from at least two reactants (normally monomers) and is inclusive of copolymers, terpolymers, tetrapolymers, and the like;
xe2x80x9cpolyolefinxe2x80x9d means a polymer in which some mer units are derived from an olefinic monomer which can be linear, branched, cyclic, aliphatic, aromatic, substituted, or unsubstituted (e.g., olefin homopolymers, interpolymers of two or more olefins, copolymers of an olefin and a non-olefinic comonomer such as a vinyl monomer, and the like);
xe2x80x9c(meth)acrylic acidxe2x80x9d means acrylic acid and/or methacrylic acid;
xe2x80x9c(meth)acrylatexe2x80x9d means acrylate and/or methacrylate;
xe2x80x9canhydride functionalityxe2x80x9d means an group containing an anhydride moiety, such as that derived from maleic acid, fumaric acid, etc., whether blended with one or more polymers, grafted onto a polymer, or polymerized with one or more monomers;
xe2x80x9coxygen permeancexe2x80x9d (in the packaging industry, xe2x80x9cpermeancexe2x80x9d often is referred to as xe2x80x9ctransmission ratexe2x80x9d) means the volume of oxygen (O2) that passes through a given cross section of film (or layer of a film) at a particular temperature and relative humidity when measured according to a standard test such as, for example, ASTM D 1434 or D 3985;
xe2x80x9clongitudinal directionxe2x80x9d means that direction along the length of a film, i.e., in the direction of the film as it is formed during extrusion and/or coating;
xe2x80x9ctransverse directionxe2x80x9d means that direction across the film and perpendicular to the machine direction;
xe2x80x9cfree shrinkxe2x80x9d means the percent dimensional change, as measured by ASTM D 2732, in a 10 cmxc3x9710 cm specimen of film when subjected to heat;
xe2x80x9cshrink tensionxe2x80x9d means the force per average cross-sectional area developed in a film, in a specified direction and at a specified elevated temperature, as the film attempts to shrink at that temperature while being restrained (measured in accordance with ASTM D 2838);
as a verb, xe2x80x9claminatexe2x80x9d means to affix or adhere (by means of, for example, adhesive bonding, pressure bonding, corona lamination, and the like) two or more separately made film articles to one another so as to form a multilayer structure; as a noun, xe2x80x9claminatexe2x80x9d means a product produced by the affixing or adhering just described;
xe2x80x9cdirectly adhered,xe2x80x9d as applied to film layers, means adhesion of the subject film layer to the object film layer, without a tie layer, adhesive, or other layer therebetween;
xe2x80x9cbetween,xe2x80x9d as applied to film layers, means that the subject layer is disposed in the midst of two object layers, regardless of whether the subject layer is directly adhered to the object layers or whether the subject layer is separated from the object layers by one or more additional layers;
xe2x80x9cinner layerxe2x80x9d or xe2x80x9cinternal layerxe2x80x9d means a layer of a film having each of its principal surfaces directly adhered to one other layer of the film;
xe2x80x9couter layerxe2x80x9d means a layer of a film having less than both of its principal surfaces directly adhered to other layers of the film;
xe2x80x9cinside layerxe2x80x9d means the outer layer of a film in which a product is packaged that is closest, relative to the other layers of the film, to the packaged product;
xe2x80x9coutside layerxe2x80x9d means the outer layer of a film in which a product is packaged that is farthest, relative to the other layers of the film, from the packaged product;
xe2x80x9cbarrier layerxe2x80x9d means a film layer capable of excluding one or more gases (e.g., O2);
xe2x80x9cabuse layerxe2x80x9d means an outer layer and/or an inner layer that resists abrasion, puncture, and other potential causes of reduction of package integrity and/or appearance quality;
xe2x80x9ctie layerxe2x80x9d means an inner layer having the primary purpose of providing interlayer adhesion to adjacent layers that include otherwise non-adhering polymers;
xe2x80x9cbulk layerxe2x80x9d means any layer which has the purpose of increasing the abuse resistance, toughness, modulus, orientability, etc., of a multilayer film and generally comprises polymers that are inexpensive relative to other polymers in the film;
xe2x80x9cseal layerxe2x80x9d (or xe2x80x9csealing layerxe2x80x9d or xe2x80x9cheat seal layerxe2x80x9d or xe2x80x9csealant layerxe2x80x9d) means
(a) with respect to lap-type seals, one or more outer film layer(s) (in general, up to the outer 75 xcexcm of a film can be involved in the sealing of the film to itself or another layer) involved in the sealing of the film to itself, another film layer of the same or another film, and/or another article which is not a film, or
(b) with respect to fin-type seals, an inside film layer of a package, involved in the sealing of the film to itself;
as a noun, xe2x80x9csealxe2x80x9d means a bond of a first region of a film surface to a second region of a film surface (or opposing film surfaces) created by heating (e.g., by means of a heated bar, hot wire, hot air, infrared radiation, ultrasonic sealing, etc.) the regions (or surfaces) to at least their respective softening points; and
xe2x80x9ccookxe2x80x9d means to heat a food product thereby effecting a change in one or more of the physical or chemical properties thereof (e.g., color, texture, taste, and the like).
Some films, including many which are used in cook-in processes, are oriented prior to use. Orientation involves stretching a film at an elevated temperature (the orientation temperature) followed by setting the film in the stretched configuration (e.g., by cooling). When an unrestrained, non-annealed, oriented polymeric film subsequently is heated to its orientation temperature, heat shrinkage occurs and the film returns almost to its original, i.e., pre-oriented, dimensions.
An oriented film has an orientation ratio, which is the multiplication product of the extent to which the film has been expanded in several directions, usually two directions perpendicular to one another. Expansion in the longitudinal direction, sometimes referred to as the machine direction, occurs in the direction the film is formed during extrusion and/or coating. Expansion in the transverse direction means expansion across the width of the film and is perpendicular to the longitudinal direction.